Hydraulic system and method of actively damping oscillations during operation thereof

Abstract

A hydraulic system and a method of actively damping oscillations during actuation of a hydraulic cylinder in a hydraulic system is disclosed. The hydraulic cylinder is actuated by energizing a motor that rotatably drives a pump. The pump supplies a fluid to the hydraulic cylinder to actuate the cylinder. A pressure of the fluid is sensed during actuation of the hydraulic cylinder. A rotational speed of the motor is varied in response to the sensed pressure of the fluid. This varying of the rotational speed of the motor actively damps pressure oscillations during actuation of the hydraulic cylinder.

1 . A method of actively damping oscillations during actuation of a hydraulic cylinder, the method comprising:
 actuating the hydraulic cylinder by energizing a motor rotatably driving a pump supplying a fluid to the hydraulic cylinder;   sensing a pressure of the fluid during actuation of the hydraulic cylinder; and   varying a rotational speed of the motor in response to the pressure of the fluid to actively damp pressure oscillations during actuation of the hydraulic cylinder.   
     
     
         2 . The method of  claim 1 , wherein the step of sensing the pressure is performed using a pressure sensor. 
     
     
         3 . The method of  claim 1 , wherein during actuation, if the pressure of the fluid is sensed to be above a target pressure, the rotational speed of the motor is reduced. 
     
     
         4 . The method of  claim 1 , wherein during actuation, if the pressure of the fluid is sensed to be below a target pressure, the rotational speed of the motor is increased. 
     
     
         5 . The method of  claim 1 , further comprising a controller that controls operation of the motor and that further receives a pressure signal from a pressure sensor indicating the pressure of the fluid. 
     
     
         6 . The method of  claim 5 , further comprising a user control in communication with the controller, the user control providing a rate signal to the controller indicating a target rate of actuation of the hydraulic cylinder. 
     
     
         7 . The method of  claim 6 , wherein the controller evaluates the pressure signal and the rate signals to determine the rotational speed at which to energize the motor. 
     
     
         8 . The method of  claim 5 , wherein, during the step of varying the rotational speed of the motor, the controller inserts a time shift to account for a response time of at least one of the motor and the pump. 
     
     
         9 . A hydraulic system comprising:
 a hydraulic cylinder;   a pump supplying a fluid to the hydraulic cylinder to actuate the hydraulic cylinder;   a variable speed motor driving the pump;   a pressure sensor sensing a pressure of the fluid; and   a controller in communication with the variable speed motor and the pressure sensor, the controller being configured to receive a pressure signal from the pressure sensor and being further configured to instruct the variable speed motor to operate at one of a plurality of speeds;   wherein, during actuation of the hydraulic cylinder, the controller evaluates the pressure signal and actively damp oscillations of the pressure of the fluid by varying the speed of the variable speed motor based at least in part on the pressure signal.   
     
     
         10 . The hydraulic system of  claim 9 , wherein the pump is a positive displacement pump. 
     
     
         11 . The hydraulic system of  claim 9 , further comprising a user control to set a target rate of actuation. 
     
     
         12 . The hydraulic system of  claim 11 , wherein the user control is in communication with the controller to provide a rate signal to the controller. 
     
     
         13 . The hydraulic system of  claim 12 , wherein the controller is configured to evaluate both the rate signal of the user control and the pressure signal of the pressure sensor in determining the speed at which to instruct the variable speed motor to operate. 
     
     
         14 . The hydraulic system of  claim 9 , wherein the pressure sensor is linked to the hydraulic cylinder. 
     
     
         15 . The hydraulic system of  claim 9 , wherein the pressure sensor is linked to a line in fluid communication with the hydraulic cylinder. 
     
     
         16 . A method of actively damping oscillations during actuation of a hydraulic cylinder by a pressure source comprising:
 sensing a pressure of a fluid actuating the hydraulic cylinder during actuation; and   adjusting the pressure source in response to the pressure of the fluid to damp oscillations in the pressure of the fluid.